How to parse all custom class names from bootstrap (or any stylesheet file) using nodejs with the css-parse package.

collect-css-classnames.js

var fs = require('fs')
  , read = fs.readFileSync
  , css_parse = require('css-parse');

var parsedCss = css_parse(read("./path/to/bootstrap.min.css", 'utf8'));
var collectedClassnames = {}

for (var i = 0; i < parsedCss.stylesheet.rules.length; ++i) {
  var rule = output_obj.stylesheet.rules[i];
  
  if (rule.selectors) {
    for (var j = 0; j < rule.selectors.length; ++j) {
      var selector = rule.selectors[j];
      var classes = selector.split(/(\s|\+|\>|\:|\[|\])+/);
      for (var k = 0; k < classes.length; ++k) {
        var classname = classes[k];
        if (classname.length > 0 && classname[0] == '.') {
          var adjacentclassnames = classname.split('.');
          for (var l = 0; l < adjacentclassnames.length; ++l) {
            var singleclassname = adjacentclassnames[l];
            if (singleclassname.length > 0) {
              collectedClassnames[singleclassname] = true;
            }
          }
        }
      }
    }
  }
}

console.log(Object.keys(collectedClassnames).sort());

Thanks for this script, however there is a little error on line 9:

var rule = output_obj.stylesheet.rules[i];

output_obj is not defined, parsedCss is.

var rule = parsedCss.stylesheet.rules[i];